Synthesis and structures of cationic bis(arene)rhenium complexes

Heating of KReO4 with benzene or its derivatives in the presence of AlCl3 and Zn gives cationic bis(arene)rhenium complexes [Re(η6-arene)2]+ (arene = benzene (1a), toluene (1b), o-xylene (1c), p-xylene (1d), mesitylene (1e)) in 30–40% yield. Similar reaction with naphthalene affords [Re(η6-naphthalene)2]+ (2) in 5% yield. The naphthalene complex 2 undergoes replacement of both ligands by tBuNC at 80 °C giving the cation [Re(tBuNC)6]+ while the benzene complex 1a does not react under these conditions. The energy decomposition analysis revealed that metal–arene bond in the cation 1a is stronger than in the neutral W(C6H6)2 but weaker than in the dication [Os(C6H6)2]2+. The structures of [1a]BF4 and [1e]BF4 were determined by X-ray diffraction.